changes to test on windows

[daniel-edwards-iress]

🔧 Changes

• Changed the way the CLI determines the config directory to use. Uses os.UserConfigDir
• Added a config file override environment variable AUTH0_CONFIG_FILE
• Created a script to run unit tests on Windows
• Added a job to GitHub actions to run unit tests on Windows

🔬 Testing

I have added unit tests and a test runner for Windows to check unit tests pass.

It should be passing the CI testing, and by running it on Windows the config will get stored in a user's config directory without a user needing to manually set a HOME environment variable.

📝 Checklist

• All new/changed/fixed functionality is covered by tests (or N/A)
• I have added documentation for all new/changed functionality (or N/A)